How do you drive a Mitchel Overdrive correctly

[ivoryjohn]

I have been assured that my current problem with my engine doesn't have anything to do with the way I drove the car. My low mileage engine developed a miss and was not firing on number three, no fire to three at all. All the standard remedies were tried, wires checked new plugs and carb but it was narrowed to the problem being a crack in the intake manifold.

The intake is being replaced but I can't help but feel that I heated the engine up , ran it real rich and that caused the really black plugs and the intake to warp and crack. This brings me to my not knowing when to shift my overdrive. I feel like I have a strong engine, Hi-c head a B carb. With all this power I wasn't afraid to put my foot into it on hills and to drive 55+ at times, mostly down hill.
But by the time I returned hone from a 60 mile run the miss could be heard and not remedied

Once I get it running strong again how do I drive it to best enjoy my over drive and the speed I had hoped for?

[Barry B./ Ma.]

Ivory John, I would run the spark lever no more than 3/4 way down and don't let the engine lug down too much on hills in overdrive, keep the rpm's up by shifting out of overdrive when she lugs. Is your radiator clean? I run mine in overdrive much of the time but don't let it lug . My temp. gauge doesn't run over 170 deg.

[Tom Wesenberg]

Did you find a crack in the intake manifold? I've never seen an intake manifold crack, other than the mounting ears when someone used a torque wrench on it.

I have seen two guys that had a miss on #3 and both times it was an internal short in the distributor cap. A new cap was installed and the engine was smooth again.

I would shift into overdrive at about 45 MPH with the stock 3.78 rear end.

BTW, if you think the Model A is geared low, my 1950 Studebaker Commander has a 4.55 rear end, but the overdrive kicks it up to 3.18, and I always used overdrive after about 35 MPH.

[TerryH]

I have had a Mitchell OD in my 1930 Town Sedan for about 8 years, along with a Snyder HC head. I was always told not to use the OD until you got to about 45 mph, which I follow. I have done quite a bit of driving with it, and even use it on fast surface streets here in S. Calif...it is so handy and easy to use. I also drive the freeways at 55-60 mph, and it will pull slight hills in OD, but I would be careful pushing it aggressively up anything more than very modest inclines. I also run with my spark about 3/4 advanced...on real level ground at 60-65 I can advance it a little more, but never fully. The worst thing you can do with the OD is to lug the engine by shifting into it going too slow, or trying to pull too steep a grade. Good luck with it and I sure enjoy mine!
Terry

[Barry B./ Ma.]

Terry, my handling gets a bit twitchy over 50, mine is a 29 with 21" wheels so I was wondering how yours handles over 50.

[ivoryjohn]

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To answer Barry my 29 Fordor is pretty well dialed in suspension wise and the streering is about as good as it gets thanks to Robert Lancaster, my Model A guru since my teen years but...I don't have shocks. When I hit a bump at high speed it feels dicey so to speak. That momentary hop over the bump can be a yeah baby experience where you wonder if you really were off the ground or if it only felt that way.

I guess I need to break down and buy the shocks arms and links. I have nothing.

[TerryH]

Barry
My 1930 Town Sedan runs very nicely at 55-60 mph without pushing it. The gentleman that I bought it from in New York spent many years totally restoring it, and made it like new. It does have shocks and a nice tight steering box, along with the stock 19" wheels. I just had new Goodyear tires installed last year, and the car tracks beautifully on surface streets or the freeway. I usually cruise at 55, and with the Mitchell, it feels very quiet and just rides very nice. Probably some of that is due to the fact that the 4 dr sedans are the heaviest Model A's, and likely damp out some of the rough spots.
Terry

[tbirdtbird]

time will tell if a replacement intake will solve your problem

[Brendan]

i have a Mitchell in my roadster with 378 gears in the rear. it also has 16 inch wheels with 6:50 tires in the rear. i cut the shifter down and i have a lever shifter for the Mitchell. also i split second gear, its easier to pick up 3rd gear i can shift the main trans and the Mitchell at the same time into 3rd low when i pull a heavy grade i pull it in second high i try to drive my car easy and not push it i have a temp gauge and a tach, the motor likes to be at about 1200 to 1800 rpm so that is where i try to keep it. the temp gauge never gets above 170. when i get going faster then 40 or so on a level road i shift into overdrive this is how i figured out how to drive my car, and i would think every Model A would be just a little different...Brendan

[John LaVoy]

There have been some problems with distributor bodies causing problems, you might want to check that. The Mitchell is a great way to go. We installed one in our sedan when we were getting set for our first big Summer Tour from California to Texas. The thing you need to be aware of is the engine rpm. You don't want to lug the engine, especially if you are running babbitt bearings. Lugging will break up the bearing. So keep your rpm up and enjoy the ride.

Regarding some of the comments about speed, the sedan in my picture is the one with the Mitchell. Someone clocked me at 75 when I was headed to the Blueridge Parkway tour. I usually run in the 50+ range but needed to get to the airport to pick my wife up who was flying to meet me in VA. If you have the shocks on, the alignment good, wheels balanced etc. you can be pretty comfortable at 50 and a little more. But the braking system is starting to be stretched at those speeds so you need to be looking at improving it and driving with an awareness of your road conditions and traffic.

[Barry B./ Ma.]

Yes, I keep thinking are those spindly 21" wheels going to hold up? Maybe I should run 30 wheels on the 29. I tried 17" (33/34), more stable but it steered harder. I never run over 55 anyway so I may leave well enough alone.